Underwater demolition package



Nov. 11, 1969 I c. w. FALTERMAN ET 3,477,373

UNDERWATER DEMOLITION PACKAGE Filed April 4, 1968 INVENTORS. CHARLES W.FALTERMAN WILLIAM J. GRIFFITH ROY MILLER ATTORNEY.

United States Patent O 3,477,373 UNDERWATER DEMOLITION PACKAGE CharlesW. Falterman, China Lake, and William J. Griffith, Inyokern, Califi,assignors to the United States of America as represented by theSecretary of the Navy Filed Apr. 4, 1968, Ser. No. 718,763 Int. Cl. F42b1/04 U.S. Cl. 102-24 2 Claims ABSTRACT OF THE DISCLOSURE The inventionherein describedmay be manufactured and used by or for the Government ofthe United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention relates to an underwaterdemolition package having its buoyancy adjusted so as to be easy forswmimmers to handle at ocean depths.

Standard underwater demolition kits known to the art are negativelybuoyant in water and thus diflicult to handle. Air bladders have beenand are presently used to reduce the negative buoyancy, but since air isvery compressible, the buoyancy of :the kits varies greatly as afunction of ocean depth. The flotation bladders are cumbersome therebylimiting the number of packages or kits one man can carry. The presentinvention provides a compact, neutrally buoyant demolition packageseveral of which may be carried by one swimmer.

SUMMARY OF THE INVENTION The present invention is for a neutrallybuoyant underwater demolition package useful at ocean depth to 200 feet.

The ordnance items in use today which are deployed through the water arefor the most part of World War II or prior with few improvements duringthe last twenty years. It is therefore an object of the presentinvention to provide an improved demolition package or assembly givingthe swimmers who are the counterpart of the Special ForcesAgency-trained Green Berets new and improved capabilities.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of the demolitionpackage in accordance with the present invention;

FIG. 2 is a section taken through 2-2 of FIG. 1;

FIG. 3 is a view partly in section of a charge used in accordance withthis invention; and

FIG. 4 is a longitudinal section of an embodiment of a charge which isused in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingthere is shown in FIG. 1 the underwater demolition assembly or packagedesignated generally by numeral 10 which comprises a haversack 11 packedwith a plurality of individual demolition charges 3,477,373 PatentedNov. 11, 1969 ICC or billets 12 which have been adjusted to a neutralbuoyancy. Haversack 11 has an overlapping flap 13 held in place by aflap tie 14. The haversack is made of gray cotton canvas treated to bewaterproof, fireproof and mildewresistant. It is provided with ashoulder strap 15 which is equipped with a snap hook 16 and fastener 17making it adjustable to any length between 20 and 50 inches. Have'rsack11 has a pocket 18 on the back which holds a plurality of synthetic foamstrips 19 (shown in section in FIG. 2) which make haversack 11 neutrallybuoyant in seawater to a depth of 200 feet. Assembly 10 can be lashed toan obstacle with the ten foot cotton securing sash cord 20 shownattached to one side of the haversack. In FIG. 2 there is shown anarrangement of synthetic foam inserts or strips 19 in the flotationpocket 18 which is an integral part of the haversack. The synthetic foamused in both the flotation pocket and in the billets to provide neutralbuoyance consists essentially of expanded, closedcell polyurethane foamwhich is formed by the treatment of a polyester (e.g., of glycerine andadipic acid) with a diisocyanate to form isocyanate groups (-NCO) at theends of the polymer chain. Other synthetic foams may be used such aspolystyrene. The foam sections were coated with a low viscosity roomtemperature vulcanizing (RTV) silicone rubber (dimethylsilicone) whichhad a water absorption percent of zero after 7 days immersion at 77 F.This coating technique effectively kept water absorption at a minimum. Apolyurethane foam piece having a density of 0.14 g./cc. or about 9lbs./ft. coated with the silicone rubber during a 6 hour period at apressure equivalent to 200 feet ocean depth showed water absorption ofless than 1% by weight.

The billets or demolition charge-s 12 were adjusted to a neutralbuoyancy to provide proper buoyancy for the assembly or package. Thereis shown in FIG. 3 charge 12 which comprises a lamination consisting ofa single longitudinal layer of synthetic foam 21 and a correspondinglayer of plastic explosive composition 22. The two layers are pressedtogether, and one end portion of a length of detonating cord orexplosive lead 23 is positioned through the center of the charge 12.Charge 12 is fitted snugly into a canvas charge bag 24 and the length'of explosive lead 23 extends through an eyelet 25 provided on the topof the charge bag and is looped under webbing 26 on one face of thecharge bag. Each charge bag 24 has a securing sash cord attached (notshown) and looped under a securing web on the other face of the chargebag. Thus, the charge and bag can be lashed to an obstacle by theswimmer. In FIG. 4 there is shown a section of another embodiment of acharge or billet 12 pressed from an explosive composition into a section22 about 6.6" long. Two synthetic foam sections 21 about 2.75" long andof the same dimensions as section 22 were cut and placed in abuttingrelation to each end of explosive section 22. A length of detonatingcord (not shown) was positioned in the center of section 22 beforepressing and then extended through the end sections 21. The charge wasthen packed into the canvas charge bag 24 for placement in thedemolition package.

The same foam used to make the haversack buoyant was used to make thebillets buoyant. The explosive compositions may vary in accordance withthe need. Explosive compositions C-3 and C-4 were used herein. They canbe shaped by hand have great shattering power. Composition C-3 contains78:2 percent cyclotrimethylenetrinitramine (RDX) and 22:2 percentexplosive plasticizer consisting of mononitrotoluene, trinitrotoluene,tetryl, and nitrocellulose.-Composition C-4 contains 91 percentcyclotrimethylenetrinitramine, 2.1 percent polyisobutylene, 1.6 percentmotor oil, and 5.3 percent di-(2- ethylhexyl)sebacate. These and othersuitable explosives are described in detail in the manual designated 3TM9-1910/TO-11A-1-34, entitled Military Explosives by the Departments ofthe Army and the Air Force, April 1955. Composition C-3 has theconsistency of putty at room temperatures between -20 F. and +125 F. Itis about 1.35 times as powerful as TNT. As the explosive charge istightly packed in the canvas charge bag, it cannot be molded into anydesired shape. It can, however, be bent or curved into close contactwith a surface that The detonating cord or explosive lead 23 is insertedinto the body of billet 12. A conventional detonating cord consisting ofpentaerythrite tetranitrate (PETN) and lead azide wrapped in a plastictubing was used. Various lightweight detonating cords of satisfactorysize may be used.

In the practice of this invention several available haversacks about 12"x 6" x 12" were made neutrally buoyant by replacing the air bladder witheleven pieces of silicon rubber-coated polyurethane foam. This reducedthe immersed weight approximately 6 /2 pounds to pound.

After remaining underwater for 3 days, the immersed weight had increasedto pound. Tests on the individual components of the system showed thatthe coated foam and explosive which formed the billets or charges gainedvery little weight when water soaked for 4 hours, while the canvasportions could be expected to gain about of a pound.

Component parts of the demolition package were soaked in water. It wasfound that in 1 /2 hours the immersed weight of the explosive charge(308 grams) had increased 3.5 percent, while the immersed weight of thecanvas sack (38 grams) had increased by 37 percent. A large canvas sack(401 grams) increased by 23 percent. After 2 /2 hours the explosivecharge (308 grams) had increased 47 percent, while the large canvas bag(401 grams) had increased 35 percent. The increase in immersed weight ofthe canvas portions of the haversack accounts for an increase of aboutof a pound.

Tests were conducted on the coated and uncoated synethetic foam sampleshaving a density of 9 pounds per cubic foot. One of each sample waspressurized in salt water to 90 p.s.i., then 140 p.s.i., 175 p.s.i. andfinally 200 p.s.i. with a hold of 15 minutes at each pressure. Theuncoated sample gained about 12 percent in weight on the first cycle andthen did not gain much more on continued cycling, and its volume shrunkby about one percent of original. The RTV silicone rubber-coated samplegained a total of about one percent over its original weight with adecrease of 0.87 percent in volume after all four pressure cycles.

The present demolition package or assembly can be floated on the surfaceof the water for towing by a swimmer. If desired, a chain of severalassemblies may be connected for towing.

Personnel swimming with this improved package report ease of carryingand handling over old types. The gain in weight at 25 feet was slightlymore than /2 pound.

What is claimed is:

1. An improved underwater demolition package which has its buoyancyadjusted to about one-fourth pound positive buoyancy at depths rangingfrom 20 to 200 feet which comprises a haversack having a pocketpositioned on the back and forming an integral part thereof, a flap typeclosure, a strap for carrying said haversack and a sash cord for lashingsaid haversack to an obstacle;

a plurality of polyurethane foam strips mounted inside said pocket, saidstrips having been coated with room temperature vulcanizingdimethylsilicone to provide minimum water absorption;

a plurality of explosive charges each fitted into an explosive chargebag and positioned in said haversack, and each of said charges beingprovided with a length of a detonating cord extending into and throughthe end thereof, the excess of said cord being looped on one face ofsaid charge bag.

2. The demolition package of claim 1 wherein each of said charges aconsists of a lamination comprising at least one layer of polyurethanefoam coated with room temperature vulcanizing dimethylsilicone and atleast one layer of a plastic explosive composition composed of 7 8 :2percent cyclotrimethylenetrinitramine and 221-2 percent explosiveplasticizer consisting of mononitrotoluene, trinitrotoluene, tetryl, andnitrocellulose.

References Cited UNITED STATES PATENTS 2,682,220 6/1954 Hagensen 102-22X 2,982,209 5/1961 Borcher 102-22 ROBERT F. STAHL, Primary Examiner US.Cl. X.R. 102-22, 97

